The present invention relates to a developing apparatus, a process cartridge and an image forming apparatus.
In an image forming apparatus such as a laser printer, an electrostatic latent image is formed on the surface of a photoconductor drum and toner is supplied to the electrostatic latent image from a developing apparatus, so that a toner image is retained on the surface of the photoconductor drum. The toner image is then transferred to a paper sheet, so that formation of an image on the paper sheet is achieved.
A developing apparatus comprises: a case having an opening faced to the photoconductor drum; a toner holder, which is blocked out in the case, for holding toner; a developing roller, which is supported at the opening of the case so as to be rotatable, for retaining toner; and a blade for regulating the layer thickness of toner to be retained by the developing roller. A portion of the surface of the developing roller is exposed from the case, and the exposed portion is in contact with and opposed to the surface of the photoconductor drum. Toner held in the toner holder is supplied onto the surface of the developing roller, carried between the blade and the surface of the developing roller with the rotation of the developing roller and retained on the surface of the developing roller as a thin layer having a constant thickness. Toner retained on the surface of the developing roller in such a manner is supplied to the electrostatic latent image formed on the surface of the photoconductor drum when the toner comes in contact with the surface of the photoconductor drum.
Such a developing apparatus is provided with toner sealing members for preventing leakage of toner from the axial end portions of the developing roller. Each of the toner sealing members is constructed by laminating a substrate portion and a felt portion which is to be frictioned with the surface of the developing roller, and is arranged so as to fold back from an opposed face, which is to be opposed to the developing roller, of a curved-face portion formed at each longitudinal end portion of the opening through the point of the curved-face portion to a face of the curved-face portion opposite to the opposed face (see Japanese Patent Application Laid-Open No. 2001-194905, for example).